Local communication networks are being designed for a wide variety of services, from telephony and broadcast television to set-top boxes, videophones and information services such as the internet. Providing these new services results in a new set of challenges to telephone and cable companies. Cable companies will have to design systems that can provide two way communication. While telephone companies will have to design a system which can simultaneously handle a variety of broadband signals.
Most likely these new services will all be provided through a single coaxial cable to the subscriber's premise. Inside the subscriber's premise a splitter will fan out a number of cable lines to the various devices needing connection to the cable system. The subscriber will be responsible for cabling within his premise, which will require a variety of splitters, connectors and couplers. Each splitter, connector and coupler is a potential source for ingress noise into the cable system. Any damage to the cable's shielding is another potential source for ingress noise.
Present, CATV systems have allocated the 5-42 MHz band for upstream signals (i.e., signals originating from the subscriber's premises). In this frequency band a wide variety of noise source exist. These include CB radios, low frequency police radios, and electromechanical devices, such as mixers. As a result, there exists an ingress noise concern for local communications networks providing a wide variety of interactive services.
One solution is to require high quality cabling within the user's premises. If all the connections were tight all the time and used high quality connectors and all unused terminals were terminated and there was no damage to the cables shielding, this would be an effective solution. However, traditionally the cabling within the subscriber's premise belongs to the subscriber and therefor it is difficult to monitor the quality and condition of the cabling.
A typical solution to noise problems in a communication system is to filter out the noise using frequency selective filters. However, this only works if the noise is in a different frequency band than the desired signal and in this case the likely noise sources are in the same frequency band as the desired signal. Thus there exists a need for a system and method to clear the desired frequency band of ingress noise before transmission of the desired signals.